Bernard,
We used to run into this type of problem when our Project files resided
on a LAN server. Occasionally the server would neglect to "release" a
file and we would get a similar message. We generally had to call IT and
have them clear the "hold".
If your file is not on a server, I would try exiting Project entirely.
If that doesn't clear it, try rebooting. If that doesn't clear it, check
your Project options settings. Go to Tools/Options/General tab and check
whether you have the option checked to open the last file on startup. If
you do, try unchecking it. If that doesn't work, the file might have
some corruption. Go to the MVP website at:
http://www.mvps.org/project/faqs.htm
and take a look at FAQ 43 - File boat? might be corruption.
If none of the above works, maybe someone else has some suggestions.
Hope this helps.
John